A number of different types of coupling piece for this purpose are already known. In particular, French patent No. 2 297 754 describes a coupling piece which is resiliently deformable, in such a way that it can be fitted between the side or lateral portions of the middle part of the main yoke of the wiper blade. In order to fit the coupling piece disclosed in the above mentioned French patent specification, lateral pressure is exerted on it, and it is then introduced into the window which is arranged in the middle portion of the main yoke of the wiper blade.
However, it has become evident that the side pressure exerted on the coupling piece tends to cause its transverse arms to break, which renders the coupling piece useless. In addition, these coupling pieces of the prior art are specific to one type of arm and to one type of wiper blade.